BUILDING DESIGN TO BE TESTED WITH FAKE QUAKE

SCRIPPS RANCH 
Engineers plan to simulate a magnitude 7.2 earthquake in Scripps Ranch on Saturday in hopes of spotting weaknesses in a type of building widely used for housing and offices.

The experiment will occur on the University of California San Diego’s outdoor shake table, which has been fitted with a 44,000-square-foot wood-frame, “soft story” structure that’s four stories high. The first floor of such buildings is left relatively open to allow for a parking garage or large windows, which makes them more vulnerable to seismic shaking.

The project is being led by Colorado State University, which has already inflicted damage on the test structure by simulating three smaller quakes meant to gauge the effectiveness of experimental retrofits. Those temblors ranged from 3.5 to 6.5 in magnitude.

Saturday’s 7.2 simulated quake is expected to produce roughly the same amount of energy released by the largest in a series of quakes that hit the Cape Mendocino area of Northern California in April 1992. That quake injured almost 100 people in Humboldt County, and it generated a small tsunami that produced 3-foot-high waves at Crescent City.

Colorado State’s John van de Lindt, principal investigator for the $1.24 million project taking place at the shake table, said: “Earthquakes are particularly damaging to buildings with open spaces at street level, and they often collapse because that first-floor parking makes the building structurally weak and soft.”

UC San Diego’s quake-simulation facility in Scripps Ranch features the world’s largest outdoor shake table.

Over the years, researchers have used testing at the site to identify ways to boost seismic safety standards. Among other things, they have helped develop stronger building materials and improved defenses against earthquake-related fires.